Devil of a Disease

State of affairs

In Terri Irwin's interview with Ray Martin, screened in Australia tonight, she made brief mention of the plight of the world's largest remaining marsupial carnivore - the Tasmanian Devil (Sarcophilus harrisii).

(Interestingly, there is a condition in humans which resembles contagious cancer - molar pregnancies occur when either an empty egg is fertilised, or a single egg receives two spem cells, and pregnancy begins, but without a normally formed foetus. In most cases the developing tissues associated with pregnancy, are aborted via miscarriage. However, in rare cases, "microscopic placental cells" may remain and "spread to other organs like cancer".)

DFTD essentially forms tumours in the face of Tasmanian devils, grotesquely altering their appearance, but more importantly, preventing the animal from properly feeding, to the point of death. In 10 to 15 years, the disease has spread to 65% of the landmass of Tasmania - an area of land estimated to contain about 80-90% of the state's pre-disease devil population. In high density population areas, this disease has resulted in up to 100% population mortality, within 12 to 18 months!. It is estimated that between 30% and 50% of the pre-disease devil population numbers have already succumbed to DFTD.

The main action plan centres around protecting remnant Tasmanian populations from exposure to the disease, further researching the disease itself, and building up offshore population stocks in zoos outside Tasmania.

How can you help?

Again, the DPIW provides information on how you can act to report sightings of Tasmanian devils and/or the disease in Tasmania.

However - if you live on the Australian mainland - and particularly in Victoria, there may be one more way you can help. Keep an eye out for devils...

Victorian devils

Yes, seriously - Victorian devils.

Robert Paddle in his book, The Last Tasmanian Tiger, reports, apart from nineteenth century sightings, that "in 1912 a live Tasmanian devil was captured at Tooborac in Victoria, and described in scientific publication by the curator of zoological collections at the National Museum of Victoria ... [and] since then the bodies of four more Victorian specimens of devil have been submitted to, preserved and catalogued by, the Mammology Department of the Museum of Melbourne - the most recent specimens being two roadkills in 1991, from localities 150 km [93 miles] apart. There would have to be a phenomenally high population of incompetent Victorian naturalists illegally keeping Tasmanian devils as pets, in order for as many as five of their lost captives to become museum specimens."

Via personal communication, the Tasmanian Department of Primary Industries and Water indicated that it believes there are no wild populations of devil in Victoria. Yet despite this, the Nomination for listing the Tasmanian Devil as a vulnerable species - presented by a member of the Tasmanian government - itself refers to these mainland populations thus:

"There have been reports of devils existing in the wild in Victoria. Sightings, footprints and five carcasses, all road casualties, have been found. The latest road kill carcass reported was in 1991 in south eastern Victoria. What is not known is whether or not the mainland population represents a sub-species or if they were deliberately or accidentally released sometime in the past."

My own question, posed to the Tasmanian Department of Primary Industries and Water earlier this year, is - if the mainland devils are also exposed to Devil Facial Tumour Disease (DFTD), but are somehow better coping with it, then don't we want to work out why?

The response was that those of the mainland devils which could be examined, "had DNA typical of those in Tasmania". This makes it much more likely that the mainland devils arrived there some time after European colonisation (as opposed to surviving beyond the accepted mainland extinction date of approximately 400-600 years before present). However - if indeed there are surviving mainland populations - even genetically identical - there is still the possibility that they are somehow more resistant to this infectious cancer.

Take as an example, a report given in May 2006, of a cancer resistant mouse. In 1999, researchers at the University of Winston-Salem, North Carolina, were "transplanting highly virulent cancer cells into mice" when it was observed "that one remarkable mouse did not develop cancer, no matter how many lethal doses it got".

The team bred the mouse, and half the offspring were also cancer-resistant.

This is still genetically a mouse. And even more interestingly, the mechanism by which introduced cancers were killed, was by a clustering of white blood cells around the tumours. "In some cases this spontaneous regression of cancer was dramatic. A very large tumour mass disappeared overnight".

Certainly, further research into mice we know are resistant to cancers is one avenue forward, but finding the mainland devils and examining them is likely to be equally important.